Leather conditioning



United States Patent 3,201,812 LEATHER CONDHTIONIN G Hubert Q. Chaplin,Leicester, England, assignor to United Shoe Machinery Corporation,Boston, Mass, :1 corporation of New Jersey No Drawing. Fiied July 25,1963, Ser. No. 297,691 (liaims priority, application Great Britain, July27, 1962, 28,854/ 62 7 Claims. (Cl. 12-146) This invention relates to amethod of conditioning leather and, more specifically, to a process ofmulling or tempering an article of leather to distribute moisturetherethrough.

The shoemaking industry has been involved throughout its history in aconstant and penetrating search for technical improvements and, inrecent years, for methods and apparatus which facilitate increasedautomation. One of the principal operations in the shoemaking cyclewhich has impeded the advancement toward complete automation is themulling or tempering of the leather. The purpose of mulling or temperingis to render the leather more workable thereby to permit flexing andstretching thereof. Thus, mulling or tempering is an importantprerequisite to a large number of shoemaking procedures.

Heretofore, a common method employed for mulling or tempering leatherhas been to house the leather in a moist atmosphere for an extendedperiod of time thereby to ensure the distribution of water throughoutthe leather. Another method of tempering leather was accomplished bydipping it in cold water for a period of hours and allowing it to drain.The result of these operations was uniformly moistened leather which waseasily worked. The procedure was, however, time consuming and,therefore, costly. Further, it did not lend itself to automation anddiluted the value of the automation of appurtenant operations. The needfor a method of mulling or tempering leather which would facilitate theintegration of these operations into an automated shoemaking cycle hasbeen long felt and desired. Adequate mulling or tempering could not besacrificed for increased automation due to the detrimental effects onoperations dependent thereon. To do so would be to thwart the purpose ofautomatation. tion is to provide an improved method of conditioningleather which materially decreases the time required for the mulling ortempering thereof.

A further object of this invention is to provide a novel method ofconditioning leather which facilitates the integration of the mulling ortempering operations into an automated shoemaking cycle.

The specific application of the subject invention hereinafter delineatedin the specification is concerned with the tempering of outsoles forwelted shoes. The subject invention is disclosed by the definition ofthis specific application in order to facilitate a complete and faciledescription thereof. However, this is not to be construed to, nor is itintended to, limit the application of this invention. The method of thesubject invention is intended for all applications wherein increasedworkability of leather or similar articles is desired.

A conventional method utilized in the manufacture of welted shoescomprises applying a coating of rubber latex to the flesh side of theoutsole to facilitate adhesion of rubber solution to the damp outsoleduring the sole laying operation, the latex being allowed to dry andcoagulate, tempering the outsole by dipping it in cold water for aperiod of from two to twelve hours, and allowing the outsole to drain.Thereafter, the operations of sole-laying, rounding and channelling, lipraising, stitching, channel laying and heel attaching are completed. Thedeficiencies stated hereinabove relative to the generic application ofthe sub- 3 ,Zh 1,8 l 2 Patented Aug. 24, 1965 ject invention are equallyapplicable tothe manufacture of welted shoes, as illustrated by theabove defined method.

Accordingly, a more specific object of the subject invention is toprovide a method of tempering outsoles during the manufacture of weltedshoes, a correlative object being a reduction of the time requiredtherefor and the adaptation thereof for integration into an automatedshoemaking cycle.

To this end and in accordance with a feature of the present invention,there is provided a method of conditioning leather comprising subjectingthe leather to a conditioning solution, applying a substantiallyimpervious or continuous coating on one side thereof, and heating thecoated side while maintaining the opposite side against a surface havinga temperature lower than that of the heat ing means.

The above and other features of the invention will now be described.

The technical phenomenon which facilitates the implementation of thesubject method is that moisture applied to one surface of a permeablearticle of manufacture can be rapidly and uniformly distributed withinthe article by the establishment of an appropriate temperature gradientthereacross. The rapidity with which the moisture is dispersed isdependent upon the temperature difference constituting the gradient, theinherent character of the article, and the condition thereof prior tothe operation. The moisture on the high temperature side of the articlewould have a higher vapor pressure than that on the low temperature sideand, thus, a pressure gradient is produced as a result of thetemperature gradient. This pressure dilferential or gradient drives themoisture into and through the article. Thus, the establishment of hotand cold sinks on opposite sides of a piece of leather or similararticle of manufacture can be utilized to distribute water or otherconditioning solutions applied to the surface subjected to the hot sink.

In the application of the subject invention in the manufacture of weltedshoes, the outsole is initially moistened by the application of aconditioning solution such as water. In the preferred embodiment, waterhaving a wetting agent therein would be employed, the wetting agentpreferably comprising sorbitol, phenol and aluminum sulphate. The solesare thereafter coated on the flesh side with rubber latex. The coatingfunctions to seal the flesh side of the outsole against loss of moistureduring the subsequent portion of the method. The coated flesh side isthereafter heated and the opposite grain side concurrently maintainedagainst a smooth flat surface such as a wooden block which constitutes acold sink. The heating means is preferably infra-red lamps or otherradiant heating elements. The tempering is accomplished in two to fourminutes and the leather remains in the tempered workable condition forapproximately one hour. The radiant heat also assists in drying andcoagulating the rubber latex employed in this particular application ofthe subject invention.

As stated above, the invention is not limited to the specificapplication defined in the preceding paragraph. Any article ofmanufacture which is permeable by water or other conditioning solutionmay be mulled or tempered by this method. Thus, upper leather can beprepared for the lasting operations by the use of this novel process.The particular conditioning solution and coating material may be variedin accordance with the requirements of the article being mulled ortempered. Rubber latex is used in the above defined procedure for weltedshoes as it additionally facilitates adhesion of a rubber solution tothe damp outsole. However, any substantially impervious or continuouscoating material which would seal the moisture in the article is equallysatisfactory.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. The method of conditioning leather comprising subjecting a leatherarticle to a conditioning medium, applying a susbtantia-llycontinuouscoating to one side surface of the leather article, and heating thecoated side while maintaining an opposite side surface at a temperaturelower than the heated side.

2. The method of conditioning leather comprising subjecting a leatherarticle to a conditioning medium, applying a substantially imperviouscoating to one side surface of the leather article, heating the coatedside, and maintaining an opposite side surface against the surface of amember having a temperature lower than the heated side during theheating thereof.

3. The method of conditioning leather comprising sub jecting a leatherarticle to an aqueous medium, applying a substantially continuouscoating to one side surface of the leather article to prevent thepassage of moisture therefrom, heating the coated side, and maintainingan opposite side surface at a temperature lower than the coated sideduring the heating thereof.

4. The method of conditioning leather comprising applying vaconditioning solution to one side surface thereof, applying asubstantially continuous coating to said side surface, and heating thecoated side surface while maintaining an opposite side surface at atemperature lower than the heated coated side thereby to cause diffusionof the conditioning solution through the leather.

5. The method of tempering leather comprising first applying aconditioning solution to a leather article, thereafter heating one sidesurface of the leather article, and maintaining an opposite side surfaceat a temperature lower than the heated side during the heating thereofto cause diffusion of the conditioning medium through the leather.

6. The method of tempering leather comprising applying an aqueous mediumto one side surface of a leather article, heating the said side surfaceby radiant heat, and maintaining an opposite side surface against thesurface of a member having a temperature lower than the heated sidethereby to cause diffusion of the aqueous medium through the leather.

7. In the manufacture of welted shoes, the method of conditioning anoutsole comprising subjecting the outsole to a conditioning medium,applying a coating of rubber latex on one side surface thereof, heatingthe coated side, and maintaining an opposite side surface at atemperature lower than the heated side during the heating thereof.

References Cited by the Examiner UNITED STATES PATENTS 2,109,425 2/ 38Hurxthal 69-21 2,421,053 5/47 Card 12--4l.5 2,586,985 2/52 Olson et a169--21 2,690,069 9/54 Kahn 69-21 JORDAN FRANKLIN, Primary Examiner.

1. THE METHOD OF CONDITIONING LEATHER COMPRISING SUBJECTING A LEATHERARTICLE TO A CONDITIONING MEDIUM, APPLYING A SUBSTANTIALLY CONTINUOUSCOATING TO ONE SIDE SURFACE OF THE LEATHER ARTICLE, AND HEATING THECOATED SIDE WHILE MAINTAINING AN OPPOSITE SIDE SURFACE AT A TEMPERATURELOWER THAN THE HEATED SIDE.